There has been known an optical device via which laser light emitted from a plurality of laser devices is combined into single outgoing light. Such an optical device is called a combiner, a coupler, or the like. For example, Patent Literature 1 discloses an optical device (referred to as “optical fiber combiner” in Patent Literature 1) including (i) a plurality of optical fibers which constitute an entrance fiber (referred to as an “input optical fiber” in Patent Literature 1), (ii) a reduced diameter part (referred to as a “bridge fiber” in Patent Literature 1) having a tapered part, and (iii) an exit fiber (referred to as an “output optical fiber” in Patent Literature 1).
Such an optical device is suitably applicable to, for example, a laser processing machine (i.e., laser system). In the laser processing machine, the optical device is used to cause laser light emitted from a plurality of laser devices to be combined into single outgoing light, so that high-power outgoing light is obtained which cannot be obtained with use of a single laser device. Such a laser processing machine is used for a processing purpose (e.g., cutting or welding) which requires the high-power outgoing light thus obtained.